1. Field of the Invention
The present invention relates to a method for sealing glass articles, more particularly a method for encapsulating an electro-luminescent element.
2. Technical Background
There is an increasing demand for OLED devices in display applications, and work is progressing toward applying OLEDs for general lighting. One drawback to the use of OLEDs has been a relatively short life when compared with more traditional light emitting diodes (LEDs). Factors which may affect the lifetime of the device include moisture and/or oxygen which may ingress into the encapsulated electro-luminescent elements of the device. As use times increase for OLED devices, the possibility of device failure due to oxidation of the electrodes, detachment of the electro-luminescent layers, or cracking of the organic elements also increases. Hermetic glass envelopes have been seen as one way in which to mitigate these effects. However, the relatively high temperatures required for sealing glass encapsulation layers to substrates may, in and of themselves, degrade the performance of the thermally sensitive organic layers of the device. Thus, there has been a widespread effort in the industry to develop more benign methods of sealing the cover glass to the substrate, such as through the use of glass frits or other non-glass adhesives such as ultraviolet (UV) cured resins. Unfortunately, non-glass adhesives have proven to be undesirable for long lifetime devices due to their permeability by moisture and out-gassing by the adhesive material. On the other hand, glass frits disposed between the substrate and the glass cover must simultaneously have a low melting temperature and have a coefficient of thermal expansion (CTE) which is closely matched to the cover glass and/or substrate.